在一堆数中查询相加得某个数的组合

   class Program
    {
         static  void Main( string[] args)
        {
             double[] numbers =  new  double[] {  258.5,  1229.1,  39.6,  660.3,  660,  660,  165,  165,  3060,  270,  4.8,  440,  279.06,  47.89,  38.02,  600,  286,  63.36,  1530,  1320,  1344,  3954 };




            Console.WriteLine( " 原数列：258.5,1229.1,39.6,660.3,660,660,165,165,3060,270,4.8,440,279.06,47.89,38.02,600,286,63.36,1530,1320,1344,3954\n\n ");


             SumFinder.FindSum(numbers,  7785.52);
             //  SumFinder.FindSum(new double[]{1,2,2,3,5}, 10);


        }
    }




     static  class SumFinder
    {
         public  static  void FindSum( double[] numbers,  double targetSum)
        {
             int elementCount = numbers.Length;
             int lastCombination =  2 << elementCount -  1;
             int firstCombination =  1;
             double sum;
             for ( int i = firstCombination; i <= lastCombination; i++)
            {
                sum =  0;
                 for ( int pos =  0; pos < elementCount; pos++)
                {
                     if ((i & ( 1 << pos)) !=  0)  // 当前组合第pos个数是否取中
                        sum += numbers[pos];
                }
                 if (sum == targetSum)
                {
                     string str =  "";
                     for ( int pos =  0; pos < elementCount; pos++)
                    {
                         if ((i & ( 1 << pos)) !=  0)
                        {
                           str += numbers[pos]+ "  +  ";
                        }
                    }
                    Console.Write(str.Substring( 0,str.Length- 3)+ "  =  " + targetSum);
                    Console.WriteLine();
                }
            }
            Console.WriteLine( " 结束 ");
            Console.ReadLine();
        }